Single aperture confocal scanning biomicroscope and kit for converting single lamp biomicroscope thereto

ABSTRACT

A single aperture confocal scanning biomicroscope is disclosed with an illumination system having a pair of lenses surrounding an aperture for collimating a field of light, a pivotally mounted flap for blocking a central portion of the light in order to create peripheral illumination, and an aperture assembly comprised of a cylindrical lens, aperture, and beam splitter which is oscillated within the light field in order to create an aperture size optical beam for scanning a patient&#39;s eye and ocular adnexae. With the illumination system of the present invention, techniques involving both direct illumination and indirect illumination may be utilized in examining the eye to produce a true confocal image thereof. Single aperture confocal scanning techniques may be brought to existing slit lamp biomicroscopes with a kit comprised simply of a pair of lenses and an aperture in one embodiment which utilizes the existing illumination system. In a second embodiment, a completely new illumination system is also utilized which provides for examination techniques utilizing both direct and indirect illumination.

This application is a continuation-in-part of application Ser. No.07/243,353 filed Sept. 14, 1988, now U.S. Pat. No. 4,884,880 to issueDec. 5, 1989; and application Ser. No. 07/243,354 filed Sept. 14, 1988,now U.S. Pat. No. 4,884,881 to issue Dec. 5, 1989.

BACKGROUND AND SUMMARY OF THE INVENTION

The slit lamp biomicroscope, or slit lamp as it is commonly referred to,is a versatile instrument used for examining the eye and ocular adnexae.It consists of a biomicroscope, an illumination source, and a mechanicalsupporting system which facilitates the positioning of the illuminationsource at various angles to the eye in order to achieve different kindsof examinations. The biomicroscope is an optical device which presentsan enlarged image of the patient's eye to the observer and may be eithera simple or compound biomicroscope with the latter having the advantagesof additional magnification and less aberration than in a single lenssystem. Most typical prior art compound biomicroscopes present a realand inverted image, which can be corrected using a prism correctionsystem. All slit lamp biomicroscopes achieve stereopsis by having aconversion angle between the separated oculars. However, there are manyoptical systems used to change magnification. These include rotatingobjectives, those that operate based on a Galilean telescope principleand those that function with zoom optics.

In examining the structures of the anterior segment of the eye, thereare four different techniques that are presently employed with the priorart slit lamp biomicroscope. The first and most common of these is thatof direct illumination. This technique involves focusing a beam of lightthrough relatively transparent media and observing the scatter of lightagainst a dark background. There are several forms of scatterillumination which are helpful in selected aspects of the ophthalmicexamination. Thus, it is useful for this type of examination to observescatter illumination in various parts of the eye.

A second technique of slit lamp examination is retro-illumination. Withthis method, light is reflected off of a diffusing surface to illuminatea more anterior structure in the eye. Thus, light may be bounced off theiris to illuminate the cornea or be reflected off of the fundus toexamine the iris or lens. The image from this technique, as well as thetechnique of direct illumination, is degraded by reflections and byscatter from objects anterior from or posterior to the plane ofinterest.

A third technique in eye examination is sclerotic scatter. In thismethod, the incident slit light beam is oriented in an oblique fashionto the eye so that light falls on the limbal area of the cornea. As theangle of incidence is greater than the critical angle, light isreflected internally along the cornea similar to light traveling infiber optic tubing. Additionally, some retro-illumination also occursdue to light scattered onto the iris or other posterior structures.While this technique is intended to visualize scars or opacities withinthe corneal stroma, the intense amount of scatter experienced reducesthe resolution of the image and, hence, the value of this technique.

A fourth technique for anterior segment examination is that of specularreflection. This method utilizes the difference in index of refractionbetween the cornea and aqueous humor or the corneatear film and air,allowing visualization of either the corneal endothelium, or epitheliumrespectively. Occasionally, the anterior and posterior surface of thelens and the zones of discontinuity within the lens can be appreciated.Specular reflection is observed only monocularly, because theillumination beam blocks one of the observation paths. The image createdwith this technique of examination is degraded due to reflections fromother portions of the corneal endothelium or epithelium or other ocularstructures. In all four of these techniques of examination, the ocularimages are also limited by the available contrast between the subject ofinterest and surrounding tissue. In addition, the closer the index ofrefraction is between the two interfaces the less the specularreflection will be, thereby reducing the amount of returning lightforming the image to be observed.

While there are accessory devices available in the prior art designed toimprove the aforementioned techniques of eye examination with the slitlamp biomicroscope, light reflection and scatter degrade thosetechniques utilizing direct illumination while limited tissue contrastand low levels of returning light limit the resolution of thosetechniques utilizing indirect illumination. Also, there is at least onetandem scanning confocal biomicroscope in the prior art which utilizesseparate apertures and light paths to achieve some improvement over thetypical slit lamp. However, difficulties of complexity and alignment areexpected to limit its usefulness, as with tandem scanning confocalmicroscopes.

To solve these and other problems with the prior art slit lampbiomicroscope, the inventors herein have succeeded in designing anddeveloping a single aperture confocal scanning biomicroscope, as well astwo variations of a kit for converting existing slit lamp biomicroscopesinto single aperture confocal scanning biomicroscopes. The manyadvantages of single aperture confocal scanning microscopy over dualaperture confocal microscopy are explained in the parent patents.Confocal microscopy includes the technique of illuminating only a smallportion of the specimen at a time, and masking the returning (reflectedor fluorescence) light to view only that same small portion to minimizethe effects of scattered and out of focus light from surroundingportions of the specimen. The entire specimen is viewed by scanning itin small increments and coalescing these increments either in real timeor with a video camera and image processor or the like. Other advantagesof single aperture confocal scanning microscopy are to be found in theparent patents referred to, supra. With this invention, the manyadvantages of single aperture confocal scanning microscopy are broughtto the instrument used to examine the eye and thereby minimize the majorproblems with the prior art slit lamp.

In one of the preferred embodiments, a significant part of the inventionincludes an improved illumination system. In the improved illuminationsystem, a set of three cylindrical lenses is used to converge the lightalong the width of the masking aperture and an additional cylindricallens positioned orthogonally to the first set is used to independentlyconverge the light along the length of the masking aperture.Incorporated in the illumination system is a single assembly comprisedof a cylindrical lens, masking aperture, and beam splitter which isoscillated as an integral unit which provides major advantages overother single aperture confocal scanning optical devices. Essentially,the illumination system includes a light filament and a curved reflectorfor concentrating a large portion of the light emanating from thefilament into a pair of lenses with an aperture positioned therebetweenin order to collimate the light into an incident light field. Thecollimating aperture is preferably a rectangular slit with cylindricallenses, although a pin hole aperture and spherical lenses can be used.With a rectangular slit, the generally rectangular filament should bealigned with its long axis parallel to the slit's long axis. This lenspair and aperture thus aid in producing an incident light field ofhighly collimated light along the width of the masking apertureutilizing a large portion of the incident light produced by thefilament. A cylindrical lens between the lens pair and aperture assemblyfocuses the incident light field along the length of the maskingaperture into a field plane thereat.

The assembly mentioned above (aperture assembly), including a lens, amasking aperture, and a beam splitter, is positioned within the lightfield beyond the last mentioned cylindrical lens and further focuses theincident light field along the width of the masking aperture into anaperture size beam at the masking aperture. Additionally, a pivotallymounted variable V-shaped flap may be used to block a variable centralportion of the light field so as to create an aperture size incidentlight beam comprised essentially of the edge portions of the lightfield. By doing so, only that light entering the lens at a relativelyoblique angle is utilized which can optimally minimize the volume ofintersection between the incident light and the return light path. Notonly does this achieve dark field illumination of the specimen but italso minimizes scattering within all planes in the return light pathwith the exception of the specimen plane. This latter feature which isachieved with this "peripheral illumination" helps to maximize opticalsectioning.

The particular lens used in the aperture assembly is a cylindrical lenswhich focuses the light along its width through the masking slitaperture. By matching the lens with the masking aperture, the aperturesize beam may actually be focused within the contour of the maskingaperture such that there is no backscatter from the aperture andvirtually all of the incident beam passes therethrough. This furtherconcentrates the incident light beam and provides a marked improvementto contrast as backscatter from the aperture is eliminated as acomponent of the light returning to the viewer. The pivotally mountedflap or peripheral illuminator may be included as part of the assemblywhich is oscillated within the conjugate field plane, if desired. All ofthe foregoing including the incident light source, lens pair andcollimating aperture, cylindrical lens focusing along the length of themasking aperture, pivotally mounted flap, and aperture assembly of lens,masking aperture, and beam splitter, all comprise the illuminationsystem which may be used to replace the slit lamp illumination system inthe prior art.

Another pair of lenses then focuses the incident light beam at thespecimen plane. Light reflected from the specimen is similarly focusedby the same lens pair at the masking aperture and is masked thereby.Thus, light returning from the specimen is masked by the maskingaperture in the preferred embodiment, but not the light illuminating thespecimen. The returning light passes through the beam splitter to abiomicroscope objective as is well known in the art and the observer isthus presented with a confocal image of the eye which is illuminatedeither with direct illumination or with peripheral illumination. As iswell known in the art, a pair of erector prisms may be used anywhere inthe return light to re-orient the image in the upright direction, andhence are not shown.

The single aperture confocal scanning biomicroscope of this inventionmay be provided as a complete device, or the illumination system andlens pair may be provided as a retrofit kit to adapt existing slit lampbiomicroscopes for use as a single aperture confocal scanningbiomicroscope.

In still another alternative, the lens used as part of the apertureassembly may be a double compound cylindrical lens; or may be a pair ofcylindrical lenses bonded together, or may be a spherical lens in theevent the cylindrical lens focusing along the length of the maskingaperture is eliminated; or the lens may focus the light only along itswidth for some applications.

A somewhat simpler embodiment is also disclosed herein comprised of anaperture, an aperture oscillator, and a pair of lenses, with analternative of a third lens or prism assembly for reinverting the image.In this embodiment, the original illumination system of a prior art slitlamp biomicroscope is utilized except that the masking aperture isplaced at the original specimen plane, and the pair of lenses are usedto refocus the incident light at a new specimen plane. Means areprovided for moving the masking aperture within the conjugate fieldplane in which it is placed. In this embodiment, the masking aperturemay have a multitude of openings through which the incident light maypass to illuminate the specimen. For example, a rotating Nipkow disc oran oscillating multi-slit aperture could be used. The third lens orerector prisms may be disposed in the returning light path to reinvertthe image for viewing by the observer. As this embodiment utilizes theexisting illumination system of the slit lamp and thus does not provideperipheral illumination, its performance is not nearly as dramaticallyimproved as with the first embodiment described above. Additionally, inthis embodiment, the mirror of the illumination system blocks a portionof the return light from the image causing resolution to suffer.Replacing the mirror with a beam splitter would prevent this blockage,but this is generally inconvenient in most biomicroscopes of prior artdesign.

While the principal advantages and features of the present inventionhave been explained above, a greater understanding of the invention maybe attained by referring to the drawings and description of thepreferred embodiment which follow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a typical prior art slit lampbiomicroscope;

FIG. 2 is a schematic representation of a prior art slit lampbiomicroscope modified for single aperture confocal scanning withoutreplacing the existing illumination system;

FIG. 3 is a schematic representation of a single aperture confocalscanning biomicroscope utilizing a replacement illumination system;

FIG. 4 is a partial cross-sectional view taken along the plane of line4--4 in FIG. 3 and detailing the masking aperture, peripheralilluminator, and collimating arrangement; and

FIG. 5 is a view taken along the plane of line 5--5 in FIG. 3 anddetailing the circular illumination limiter adjacent the maskingaperture.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown in FIG. 1, a typical slit lamp biomicroscope of the prior artincludes an illumination system 20 comprised of a light filament 22,three lenses 24 and a pair of apertures 26 for adjusting the incidentlight, a mirror 28 which is substantially narrow and rectangular fordirecting the light through an objective lens 30 onto a patient's eye32. Returning light passes around the rectangular mirror 28 and into theviewing optics 34 for viewing the image of the eye 32. The illuminationsystem 20 is generally mounted on a traverse rod or the like so that itcan be oriented at various angles to the patient's eye 32 in order toprovide for either direct illumination of the eye 32 or indirectillumination of the eye as is explained in the background of theinvention, supra.

As shown in FIG. 2, the simplest way to convert the prior art slit lampbiomicroscope of the prior art as shown in FIG. 1 for single apertureconfocal scanning is by the simple addition of several lenses, anaperture, and an aperture oscillation device. As shown therein, the sameillumination system 20 is utilized comprised of the filament 22, lenses24, apertures 26, mirror 28, and objective lens 30. However, an aperture36 is positioned at the focal plane whereat the eye 32 was previouslylocated and a pair of lenses 38 are used to focus the incident lightinto a new specimen plane whereat the eye 32 is repositioned and thereturning light at a field plane coincident with the aperture. Anaperture oscillation or rotation device 40, as is well known in the art,moves the aperture 36 to scan the eye 32 with light from theillumination system 20, with both incident and reflected lighttraversing the same aperture 36 to thereby produce a confocal image ofthe eye 32. The same viewing optics 34 are used to observe the image.The lenses 38 and aperture 36 may be mounted in a fixed positionrelative to the patient, in which event a limited amount of lateralmovement of the illumination system 20 may be permitted for a limitedexamination with indirect illumination. Therefore, eye examinationtechniques utilizing indirect illumination may be performed with thisarrangement. However, backscatter of light from aperture 36 limitscontrast and would have to be corrected with polarizers.

Another embodiment is depicted in FIGS. 3-5 and includes a completelynew illumination system 42. The illumination system 42 is comprised of alight filament 44 partially surrounded by a curved reflector 46 whichshines a field of incident light into a light collimating arrangement48. The light collimating arrangement 48 includes a pair of lenses 50,52 separated by an aperture 54, with lens 50 focusing the incident lightthrough the aperture 54 and lens 52 defocusing the light into acollimated incident light field of parallel light 56. As shown in FIGS.3 and 4, lenses 50, 52 are cylindrical lenses and aperture 54 is arectangular slit. With this arrangement, incident light is collimatedalong the width of collimating aperture 54. However, in an alternativeembodiment, lenses 50, 52 may be spherical lenses and aperture 54 may bea pin hole instead of a rectangular slit. With this arrangement,incident light is highly collimated along both the width and length ofmasking aperture 66. Cylindrical lens 57 focuses the collimated lightfield 56 along the length of masking aperture 66.

A peripheral illuminator 58 is generally comprised of a pivotallymounted variable V-shaped flap 60 which can be used to block a variablecentral portion of the collimated light field 56. This would provide forperipheral illumination, as is explained above. An aperture assembly 62is generally comprised of a cylindrical lens 64 and a rectangular slitaperture 66 joined at their edges with a beam splitter 68 completing thetriangle. The aperture assembly 62 may be oscillated within the plane ofthe aperture 66 by an oscillator 70, as is well known in the art.Additionally, peripheral illuminator 58 may be physically secured toaperture assembly 62, or not, depending upon the particular application.Cylindrical lens 64 serves to focus the light field 56 along its widthand thereby produce a generally rectangular incident aperture beam whichclosely approximates the contour of masking aperture 66, but remainswithin its contour to thereby pass therethrough without masking thereby.Cylindrical lenses 57 and 64 focus the light field 56 at a field planecoincident with masking aperture 66 which is conjugate to the specimenplane 72 whereat the eye 74 is positioned. A circular illuminationlimiter 75 is mounted adjacent masking aperture 66 and is used torestrict the illumination to a circular field. As shown in FIG. 4, theaperture size beam 76 fits within the rectangular slit aperture 66. Apair of lenses 78, 80 focus the incident light at the specimen plane 72whereat the eye 74 is positioned and returning light at a field planecoincident with the aperture such that the aperture size beamilluminates only an aperture shaped portion of the eye. As shown in FIG.5, the circular illumination limiter 75 remains fixed as the apertureassembly 62 moves to scan the specimen 74. FIG. 5 depicts the maskingachieved by limiter 75 at three different positions of the oscillatingaperture assembly 62. In order to examine different portions of the eye,all of the components of the single aperture confocal scanningbiomicroscope may be moved about the eye while a patient rests his chinin a fixture, as is well known in the art. The specimen plane 72 isbeyond the standard specimen plane of the standard biomicroscope.

As is evident from the foregoing, with the present invention as shown inFIGS. 3--5, an existing slit lamp biomicroscope may be modified byproviding a new illumination system 42 as well as one or both of lenses78, 80 in order to convert it to a single aperture confocal scanningbiomicroscope. Alternately, completely new single aperture confocalscanning biomicroscopes may be provided using the features of thepresent invention.

There are various changes and modifications which may be made to theinvention as would be apparent to those skilled in the art. However,these changes or modifications are included in the teaching of thedisclosure, and it is intended that the invention be limited only by thescope of the claims appended hereto.

What is claimed is:
 1. In a device having means for producing a confocalimage of a desired object positioned at an object plane, the improvementcomprising a light source having means for producing non-collimatedlight, means for collimating a substantial portion of the light fromsaid light source in at least one orientation into a light field, andmeans for focusing a substantial portion of said collimated light fieldinto an aperture shaped beam at a field plane conjugate to the objectplane so that as the focusing means is moved the aperture shaped beamconfocally scans the object.
 2. The device of claim 1 wherein thecollimating means includes a pair of lenses and a collimating aperturepositioned between said lenses so that one of said lenses focuses theincident light into the collimating aperture and the other of saidlenses de-focuses the light emerging from the collimating aperture intothe light field.
 3. The device of claim 2 wherein the collimatingaperture is approximately in the shape of a rectangular slit and thelens pair are two cylindrical lenses.
 4. The device of claim 2 whereinthe collimating aperture is approximately in the shape of a pin hole andthe lens pair are two spherical lenses.
 5. The device of claim 2 furthercomprising a masking aperture in the returning light path and whereinthe focusing means includes means for focusing the aperture shaped beamat the masking aperture so that substantially all of the aperture shapedbeam passes therethrough.
 6. The device of claim 5 wherein the maskingaperture and the aperture shaped beam are substantially in the shape ofa rectangle, and the focusing means includes means for focusing thecollimated light field along both the width and length of the rectangle.7. The device of claim 6 wherein the focusing means includes at leasttwo orthogonally oriented cylindrical lenses.
 8. The device of claim 5further comprising means for maintaining register between said maskingaperture and the aperture shaped beam as the aperture shaped beam scansthe object.
 9. The device of claim 8 wherein said register meanscomprises a mechanical connection between said masking aperture and thefocusing means.
 10. The device of claim 9 further comprising means forselectively blocking a portion of said light field from said focusingmeans.
 11. The device of claim 9 wherein the blocking means includesmeans for varying the amount of said light field portion blockedthereby.
 12. The device of claim 11 wherein the blocking means comprisesa flap pivotally mounted in the light field.
 13. The device of claim 12wherein the flap is mounted in substantially the center of the lightfield so that all but the edge portions of the light field may beblocked from the focusing means, and further comprising means formaintaining register with at least a portion of the focusing means asthe focusing means is moved to scan the object with the aperture shapedbeam.
 14. A confocal, scanning, biomicroscope for examining a human eye,said biomicroscope having both an incident light path and a returninglight path, means for producing a single field plane conjugate to theeye under examination in both the incident and the returning lightpaths, and a single aperture positioned at said conjugate field plane,said aperture having means for masking at least the returning light tothereby produce a confocal image of the human eye.
 15. The biomicroscopeof claim 14 wherein the field plane producing means includes means forfocusing at least a portion of the incident light into an apertureshaped beam substantially the same shape as the aperture.
 16. Thebiomicroscope of claim 15 further comprising means for processing theincident light for peripheral illumination of the eye.
 17. Thebiomicroscope of claim 16 wherein the peripheral illumination meanscomprises means for blocking at least a portion of the focusing meansfrom the incident light except that portion thereof which illuminatesits edges.
 18. The biomicroscope of claim 17 wherein the blocking meanscomprises a pivotally mounted flap.
 19. The biomicroscope of claim 16further comprising means for maintaining alignment between the focusingmeans, peripheral illumination means, and aperture as they are moved tothereby scan the eye with the aperture shaped beam.
 20. Thebiomicroscope of claim 19 wherein the aperture is in the approximateshape of a rectangular slit and the focusing means comprises acylindrical lens.
 21. The biomicroscope of claim 19 wherein the focusingmeans has means for focusing incident light through both the height andwidth of the aperture.
 22. The biomicroscope of claim 14 furthercomprising an incident light source having means for producingnoncollimated light, means for collimating a substantial portion of thelight from said light source in at least one orientation into a lightfield, and means for focusing a substantial portion of said collimatedlight field into an aperture shaped beam at the conjugate field plane sothat as the focusing means is moved the aperture shaped beam confocallyscans the eye.
 23. The biomicroscope of claim 22 wherein the collimatingmeans includes a pair of lenses and a collimating aperture positionedbetween said lenses so that one of said lenses focuses the incidentlight into the collimating aperture and the other of said lensesde-focuses the light emerging from the collimating aperture into thelight field.
 24. The biomicroscope of claim 23 wherein the collimatingaperture is approximately in the shape of a rectangular slit and thelens pair are two cylindrical lenses.
 25. A confocal, scanningbiomicroscope having means for producing an image of a desired portionof a specimen, and means for generating an incident light beam capableof peripheral illumination of the specimen.
 26. The biomicroscope ofclaim 25 wherein the incident light beam generating means includes alight source, and the peripheral illumination means includes means forblocking the central portion of said incident light source.
 27. Thebiomicroscope of claim 26 further comprising means for varying theproportion of the incident light source which is blocked.
 28. Thebiomicroscope of claim 27 wherein the blocking means comprises apivotally mounted flap.
 29. In a confocal, scanning optical device, theimprovement comprising an incident light source having means forgenerating a ray-annular shaped peripheral illumination incident lightbeam.
 30. The device of claim 29 wherein the non-annular shapedperipheral illumination means includes means for blocking the centralportion of the incident light source.
 31. The device of claim 30 furthercomprising means for varying the proportion of the incident light-sourcewhich is blocked.
 32. In a single aperture, confocal, scanning opticaldevice having means for producing a confocal image of a desired objectpositioned at an object plane, the device having means for focusing theincident light and the reflected light at a field plane conjugate to theobject plane, the single aperture being positioned at said conjugatefield plane, the improvement comprising the focusing means having meansfor focusing substantially all of said incident light beam inside theedge of said aperture so that said incident light beam passestherethrough with minimal masking by said aperture.
 33. The device ofclaim 32 wherein said focusing means includes means for focusing saidincident light beam into substantially the same shape but slightlysmaller than the aperture as it passes therethrough.
 34. The device ofclaim 33 wherein the shape of the aperture and the incident light beamis substantially that of a rectangular slit, and the focusing meansincludes means for focusing the incident light along both the width andheight of the single aperture.
 35. The device of claim 34 wherein thefocusing means includes at least a pair of orthogonally orientedcylindrical lenses.
 36. The device of claim 32 further comprising meansfor producing an incident light field of substantially collimated light,and means for moving at least a portion of said focusing means withinsaid light field to thereby scan the object with incident light.
 37. Ina single aperture confocal scanning optical device having means forproducing a confocal image of a desired object positioned at an objectplane, the single aperture being positioned at a field plane conjugateto the object plane in at least the return light path, the improvementcomprising means for focusing an incident light beam into substantiallythe same contour as the aperture at the object plane without masking byan aperture with an equivalent contour.
 38. The device of claim 37further comprising means for producing a light field of collimated lightand means for moving at least a portion of said focusing means withinsaid light field to thereby scan the object with the incident lightbeam.
 39. The device of claim 38 further comprising means forcoordinating the movement of said focusing means portion and theaperture as said object is scanned.
 40. The device of claim 39 furthercomprising means for converting said light beam into a peripheralillumination beam.
 41. The device of claim 32 wherein said focusingmeans focuses the incident light beam through the aperture.
 42. In asingle aperture confocal scanning optical device, the device having alight source for producing collimated light, an incident light path, anda return light path, the improvement comprising an assembly positionedin both the incident light path and the return light path, said assemblyhaving means for focusing the collimated light into a beam which maypass through an aperture, said assembly including the aperturepositioned at least in the return light path for masking the returnlight, and means for moving said assembly within the collimated light tothereby scan the object and create a confocal image thereof.
 43. Thedevice of claim 42 wherein the assembly further comprises a beamsplitter extending between the focusing means and the aperture.
 44. Thedevice of claim 42 wherein the assembly further comprises means forpartially blocking the incident light path to thereby restrict thecomposition of the incident light beam.
 45. The device of claim 44wherein the blocking means includes means for selectively blocking avariable central portion of the incident light path to thereby restrictthe composition of the light beam to edge lighting.
 46. The device ofclaim 42 wherein the focusing means includes means for focusing the beaminto substantially the same contour as that of the aperture.
 47. In abiomicroscope having means for producing a confocal image of an objectpositioned at an object plane, the biomicroscope including means forfocusing the incident light along an incident light path and means forfocusing the light returning rom the object along a return light path,the improvement comprising means for substantially eliminating anyintersection between the incident light and the return light, except atthe object plane.
 48. The biomicroscope of claim 47 wherein the lightintersection eliminating means comprises a peripheral illuminatorpositioned in the incident light path.
 49. The biomicroscope of claim 48further comprising means to adjust the peripheral illuminator to therebyadjust the intersection of light to a minimum.